A container, e.g., a freight container or a cargo container, is a quadrangular parallelepiped metal box that is often used to transport maritime cargo. As shown in FIG. 1, a plurality of containers, for example, upper and lower containers C1 and C2, need to be stacked in multiple stages during transport or storage.
In this case, conventional container-fastening devices 1 that are called twist locks are devices for fastening the upper container C1 with the lower container C2. As shown in FIG. 2, each of the conventional container-fastening devices 1 includes a main body 6, a first coupling member 7 that is provided on an upper end portion of the main body 6 to be rotatable between a locked position and an unlocked position and is detachably inserted into a bottom hole 4 that is formed in a bottom surface of a corner member 2 that is disposed at a lower corner of the upper container C1, and a second coupling member 8 that is provided on a lower end portion of the main body 6 to be rotatable between the locked position and the unlocked position and is detachably inserted into an insertion hole 5 that is formed in a top surface of a corner member 3 that is disposed at an upper corner of the lower container C2.
Assuming that the conventional container-fastening devices 1 are used, the upper and lower containers C1 and C2 are fastened to each other when a worker rotates the first coupling member 7 that is inserted into the bottom hole 4 and the second coupling member 8 that is inserted into the insertion hole 5 to the locked position, and in contrast, the upper and lower containers C1 and C2 are separated from each other when the worker rotates the first coupling member 7 and the second coupling member 8 to the unlocked position.
However, since the conventional container-fastening devices 1 are devices separate from the upper and lower containers C1 and C2, and thus are used when necessary after being separately stored apart from the upper and lower containers C1 and C2, it is inconvenient to store the conventional container-fastening devices 1 and there is a high risk of the conventional container-fastening devices 1 being lost during storage.
Also, since the first coupling member 7 and the second coupling member 8 have to be accurately disposed on and then respectively inserted into the bottom hole 4 and the insertion hole 5 of the corner members 2 and 3, it is not easy to fasten the upper and lower containers C1 and C2 of the conventional container-fastening devices 1, thereby increasing working hours.